How to Tie a Double Uni Knot

By Brett Mensforth

We’re regularly asked technical questions by our readers and Facebook friends, and one of the most common queries is how best to join braided line to monofilament leader. Anyone fishing with braid and not using swivels or other connectors really needs to know at least one reliable joining knot. Incorporating a length of nylon or fluorocarbon leader into your fishing system will provide several advantages, such as adding a small amount of stretch, improving abrasion resistance at the business end and separating the highly visible braid from lure or hook.

There are several knots to choose from and some are definitely better than others, but one stands alone for ease of tying and all round reliability – the back-to-back or double uni knot.

I should point out here that some of the more complex braid to mono knots, such as the FG and Slim Beauty, are undoubtedly better suited to some gamefishing situations and heavy line. However, the double uni offers a broad spectrum of applications and is ideal from lines from ultra light up to around 15kg.

As its name suggests, the double uni consists of two uni knots that are formed and then brought together from opposite directions until they meet and lock. It’s a simple process that takes just minutes to learn and master. We all know how strong and reliable the single uni knot is when used to tie on a hook or connect mainline to a swivel, and this reliability is maintained when there are two uni’s forming a braid to mono connection.

There are a few things to consider when attempting to tie a double uni, the most significant of which is the diameter differential between braid and leader. Ideally, the double uni works best when the leader material (nylon monofilament or fluorocarbon) is no more than three times the breaking strain of the braid mainline. When the diameter of the leader is substantially more than the braid (such as 15kg leader to 3kg braid), joining the two is a tad more difficult and less reliable.

Having said that, however, there is a way around the different diameter problem. By doubling the end of the braid, you can expect to tie a good, strong double uni. Essentially, you’re presenting six kilo braid (2x3kg) instead of a single strand, which narrows the diameter gap between braid and leader dramatically. I use this variation regularly when fishing light tackle for things like big flathead, school mulloway or snapper that really do call for robust leader.

As a rule of thumb, I like to have around two rod lengths of mono or fluorocarbon in the system if possible, but may have to go a bit shorter in some lure casting situations. In this case I’ll attach a leader that allows the double uni connector to remain just outside the reel spool when the lure is ready to cast, ensuring the knot doesn’t get caught up in the process.

As already mentioned, the double uni knot isn’t at all difficult to tie. Here’s a step-by-step look at how to form it correctly. We’ve used some cord in the following images, as it’s a lot easier to photograph and, hopefully, easier for you to see. However, it doesn’t tie anywhere as neatly as braid or monofilament, so you’ll have to forgive the few lumps and bumps in the finished knot. The number of wraps has also been reduced to make things easier to tie in the cord.

The white cord represents the braid and the black represents the leader.

Step 1

Once you’ve chosen your leader length and breaking strain, lay it across the end of your braid mainline so you have at least 30cm of each to work with. If you’re intending to connect leader that’s more than three times heavier than your braid, double the end of the braid for 30cm.

Step 2

Make a decent sized loop in the braid and pinch the side of the loop nearest the leader so that it sits along the leader. The tag end of the braid should be facing away from the knot.

Step 3

Keep that pinch with your left hand, then wrap the tag end of the braid around the both the leader and the side of the loop neatly at least seven times.

Step 4

Once you’ve completed the wraps, slowly pull the tag end of the braid and draw the loop up. The wraps will gradually be brought together. You don’t need to pull the knot tight at this stage.

Step 5

Now turn the knot around 180 degrees so that you can make a loop in the leader and lay it alongside the braid. This is exactly what you did earlier, but this time you’ll be wrapping the leader around the braid. Continue the wrapping process as in steps 3 and 4, except with the leader and braid reversed.

Step 6

You now have two loose uni knots that are separated by a few centimetres of braid and leader material. The final step is to slowly and evenly pull the two knots toward each other. It’s a good idea to lubricate the leader and braid between the knots with some saliva prior to doing this, as resultant friction may cause heat build up.

Step 7

When the two knots are butted right up against each other, it’s time to tighten them completely. Grab the braid at the end of one knot and the leader at the end of the other apply steady pressure in opposite directions. This will tighten the whole system.

Step 8

Finally, using a sharp blade, trim the tag ends off with a couple of millimetres of each end. The completed knot should look like a continuous barrel that is quite small in profile and super strong. If you’re really fussy, you can dab some super glue on the knot, but I rarely bother. It should run smoothly through the rod guides and provide excellent connection strength.

As is the case with just about every fishing knot, the completed double uni should look neat once pulled tight. If your wraps have bunched up while being drawn together or the knot appears bulkier than it should, chances are it’s not as strong and reliable as it could be. It’s a quick one to tie, so cut it off and start again if you have any doubts!